Intake air filter for an internal combustion engine

ABSTRACT

An intake air filter ( 1 ) is for an internal combustion engine, especially in a motor vehicle. The filter has a filter housing ( 2 ) having a raw air inlet ( 4 ), a pure air outlet ( 5 ), and an annular filter element ( 3 ) which is arranged in the filter housing ( 2 ) and through which air can flow in a radial manner from the outside towards the inside. The filter element has a first end disk ( 10 ) on the axial end thereof, said disk has an opening ( 12 ) by which means the pure air outlet ( 5 ) communicates with the inside ( 8 ) of the annular filter element ( 3 ). The purpose is to reduce the influence of a secondary air induction on the fresh air supply of the internal combustion engine. To this end, the filter housing ( 2 ) has a secondary air outlet ( 6 ), on the pure air side, and the annular filter element ( 3 ) has a second end disk ( 11 ) on an axial end opposing the first end disk ( 10 ). The second end disk has at least one opening ( 17 ) by which the secondary air outlet ( 6 ) communicates with the inside ( 8 ) of the annular filter element ( 3 ).

CROSS REFERENCE TO RELATED APPLICATIONS

Applicant claims priority under 35 U.S.C. §119 of German Application No.101 59 097.0 filed Dec. 1, 2001. Applicant also claims priority under 35U.S.C. §365 of PCT/DE02/04336 filed Nov. 26, 2002. The internationalapplication under PCT article 21(2) was not published in English.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an intake air filter for an internalcombustion engine, in particular in a motor vehicle.

2. The Prior Art

Such an intake air filter is known, for example, from German Patent DE39 34 433 C2 and has filter housing which has a crude air inlet and aclean air outlet. In this filter housing, the intake air filter containsa ring filter insert through which the air flows radially from theoutside to the inside during operation and which has a first end diskcap on one axial end. This first end disk is designed as an opened enddisk and thus has a central opening through which an outlet connectionformed on the clean air outlet of the filter housing passes through thefirst end disk so that the clear air outlet communicates with theinterior of the ring filter insert on the clean side through the openingin the first end disk. A second end disk of the ring filter insertdesigned on one axial end facing away from the first end disk isdesigned as a closed end disk.

Such an intake air filter is used to supply an internal combustionengine with purified fresh air and forms a part of an intake tract ofthe internal combustion engine. With certain internal combustionengines, air may be injected into the exhaust line of the internalcombustion engine with the help of a secondary air supply, for examplein order to perform a secondary oxidation of the combustion exhaustgases in the exhaust line in order to reduce emissions. Purified freshair which branches off from the intake tract of the internal combustionengine downstream from the intake air filter is normally used for thispurpose. Likewise, fresh air purified with the help of a secondary airsupply may also be needed for other purposes, e.g., regeneration of aparticle filter. Since the intake tract of an internal combustionengine, e.g., in a motor vehicle, is usually also designed to attenuatethe sound that occurs during operation, an additional branch lineconnected to the fresh air line may have a negative effect on noiseoptimized tuning of the intake system. Furthermore, activation of asecondary air fan causes a drop in pressure in the fresh air tract whichmay have a negative effect on fresh air supply to the internalcombustion engine.

SUMMARY OF THE INVENTION

The present invention has as an object providing a means of reducing theinfluence of the diverting the secondary air on the tuning of the freshair system for an internal combustion engine having a secondary airsupply.

This object is achieved according to the present invention.

This invention is based on the general idea of diverting the secondaryair as early as at the filter housing by mounting a secondary air outletthere which communicates in the interior of the filter housing with theinterior of the ring filter insert through a second end disk of the ringfilter insert which is opposite the first end disk. Due to this design,the secondary air is removed on the clean side of the ring filterinsert, but the additional removal of air does not take place downstreamfrom the filter housing but instead occurs already in the filterhousing. A pressure drop which may optionally occur in activation of thesecondary air intake-may then have little or no effect on the intaketract of the internal combustion engine downstream from the filterhousing, first because the flow path to the crude air inlet of thefilter housing with the design according to this invention is relativelyshort and second, the crude air inlet of the filter housing may bedesigned to be large accordingly so that there is no throttling at thispoint which would encourage a pressure drop. In addition, the design ofthe intake air filter according to this invention permits a novel formof guidance for the intake line of the secondary air supply which may beadvantageous for certain applications.

According to an advantageous embodiment, a connection may be provided onthe second end disk so that the secondary air outlet of the filterhousing communicates with the interior of the ring filter insert throughthis connection. This design makes it possible to greatly simplify theinstallation of the ring filter insert equipped with this connection inthe filter housing. At the same time this yields a simple design of thefilter housing.

Essentially it is possible to manufacture the connection and the secondend disk as separate components, in which case the connection is theninserted into the second end disk and/or is fixedly connected to itand/or is welded or glued to it. This design permits a choice ofmaterials that is optimized as to function for the components that areproduced independently of one another.

As an alternative, the connection may be manufactured separately fromthe second end disk, in which case then the connection is fixedly moldedor foamed into the second end disk by injection molding or foaming atthe time of manufacture of the second end disk. This design also permitsa differentiated choice of materials for the two components, whereby theconnection is integrated into the second end disk in its manufacture inorder to thereby form an inseparable unit. This type of manufacturingeliminates assembly of the connection on the end disk and alsoeliminates the need for sealing measures.

In a particularly advantageous alternative embodiment, the connectionmay be integrally molded onto the second end disk. This means that theconnection and the second end disk are manufactured as a single part, inparticular in one injection molding operation. This design can beimplemented in a particularly inexpensive manner is advantageouslysuitable for mass production.

According to a special refinement, a secondary outlet connection may beformed on the filter housing, this outlet connection being designed tobe complementary to the connection of the second end disk andcommunicating with the interior of the ring filter insert through thesecondary air outlet. The secondary air outlet connection forms anextension of the secondary air outlet in the interior of the filterhousing. With the help of such a secondary outlet connection, asufficiently well-sealed communicating connection between the secondaryair outlet and the interior of the ring filter insert can be implementedin a particularly simple manner. Furthermore, through a suitablearrangement of such a secondary outlet connection, installation of thering filter insert in the filter housing can be simplified, which isadvantageous in initial assembly as well as when replacing the ringfilter insert.

Here again, it is expedient to design the secondary outlet connection asan integral part of the filter housing, so that a relatively inexpensiveone-piece production becomes possible, e.g., by an injection moldingprocess.

Installation of the ring filter insert into the filter housing may alsobe simplified by the fact that the secondary outlet connection of thefilter housing and the connection of the second end disk cooperate inthe manner of a plug connection when the ring filter insert is insertedinto the filter housing.

Other important features and advantages of this invention are derivedfrom the subclaims, the drawings and the respective description of thefigures on the basis of the drawings.

It is self-evident that the features mentioned above as well as those tobe described below can be used not only in the combination indicated butalso in other combinations or alone without going beyond the scope ofthe present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred exemplary embodiment of this invention is depicted in thedrawings and is explained in greater detail in the followingdescription, where the same reference notation refers to the same orfunctionally identical or similar components.

The only FIGURE is FIG. 1, which shows a sectional view through anintake air filter according to this invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

According to FIG.1, an inventive intake air filter 1 has a filterhousing 2 and a ring filter insert 3 accommodated therein. The intakeair filter 1 forms a component of a fresh air tract (not otherwiseshown) of an internal combustion engine (also not shown), in particularin a motor vehicle. The filter housing 2 has a crude air inlet 4 whichusually communicates with the ambient air of the internal combustionengine. In addition, the filter housing 2 contains a clean air outlet 5through which the filtered fresh air goes to the combustion chambers ofthe internal combustion engine. The inventive filter housing 2 is alsoequipped with a secondary air outlet 6 which can be connected to asecondary air supply (as not shown) of the internal combustion engine.

The ring filter insert 3 separates a crude space 7 which surrounds thering filter insert 3 from a clean space 8 formed by the interior of thering filter insert 3 in the interior of the filter housing so that whenthe reference number 8 is used below it is understood to also refer tothe interior of the ring filter insert 3. In this design, a ring-shapedfilter body 9 of the ring filter insert 3 has air flowing through itradially from the outside to the inside. The ring filter insert 3 has anend disk on each of its axial ends, namely a first end disk 10 and asecond end disk 11.

The first end disk 10 is assigned to the clean air outlet 5 and containsa central opening 12 through which the clean air outlet 5 communicateswith the interior 8 of the ring filter insert 3. In the embodiment shownhere, a main outlet connection 13 is formed on the filter housing 2 inthe area of the clean air outlet 5, so that the ring filter insert 3 canbe placed on it with the opening 12 of the first end disk 10. In doingso, an axially protruding ring 14 then penetrates into the opening 12 inthe first end disk 10. When the ring filter insert 3 is completelyplaced in position, the first end disk 10 is in contact in the insertiondirection with a peripheral collar 15 protruding radially, the collarbeing formed on the main outlet connection 13 and being closed in theperipheral direction. Corresponding sealing means (not shown here)ensure adequate sealing of the clean side 8 with respect to the crudeside 7. The main outlet connection 13 can be manufactured separatelyfrom the filter housing 2 and connected at 13, in particular by a weldor a glued connection.

Like the first end disk 10, the second end disk 11 is also designed asan open end disk and includes a central opening 17 through which thesecondary air outlet 6 communicates with the interior 8 of the ringfilter insert 3. In the area of this central opening 17, a connection 18is inserted into the second end disk 11. For example this connection 18may be designed by injection and/or foaming around a core and/or in onepiece with the end disk material in the manufacture of the second enddisk 11 in a suitable manner, so that the connection 18 forms apermanent part of the second end disk 11. In the embodiment shown here,in the case of a ring filter insert 3 inserted into the filter housing2, the connection 18 is bent at an angle and/or curved and connected sothat it communicates with a secondary air outlet connection 19. Thissecondary outlet connection 19 is designed on the inside of the filterhousing 2 and is connected to the secondary air outlet 6 so that theycommunicate and/or the secondary outlet connection 19 forms thesecondary air outlet 6 on its end which faces away from the connection18. The secondary outlet connection 19 is expediently manufactured inone piece, i.e., integrally with the filter housing 2, e.g., by aninjection molding process.

In the embodiment shown here, the connection 18 and the secondary outletconnection 19 come to rest on one another in the axial direction in thecase of the ring filter insert 3 inserted into the filter housing 2,with sealing agents 20 that act axially being provided to also seal theclean space 8 with respect to the crude space 7 in the area of thesecond end disk 11.

An embodiment in which the connection 18 and the secondary outletconnection 19 cooperate in the manner of a plug connection is preferred,in which case a radial gasket may be then be provided in particular.

It is likewise possible to design one of the connections 18 or 19 with aconical shape, in which case then the other connection will have acomplementary receptacle. This design also simplifies the manufacture ofa tight coupling between the two connections 18 and 19.

In another embodiment, one of the connections, e.g., the secondaryoutlet connection 19, may be equipped with a displaceable sleeve whichis displaceable in the axial direction on the outer jacket of thesecondary outlet connection 19. When the sleeve is pushed back, it isadjusted in the direction of the secondary air outlet 6 to therebyfacilitate the installation and removal of the ring filter insert 3.When the ring filter insert 3 is inserted, then an end of the connection18 which faces the secondary outlet connection 19 comes to rest axiallyon the facing end of the secondary outlet connection 19, in which casethen the sleeve can be pushed over the mutually abutting axial ends ofthe connections 18 and 19 to thereby ensure a sufficiently tightcoupling between the two connections 18 and 19.

During operation of the internal combustion engine, unfiltered fresh airflows through the crude air inlet 4 into the filter housing 2, goingfrom there into the interior 8 of the ring filter insert 3 and comingout of the filter housing 2 through the clean air outlet 5. This freshair flow is generated by a vacuum created by the internal combustionengine and applied to the clean air outlet 5. When the secondary airsupply is deactivated, a secondary air line (not shown) which isconnected to the secondary air outlet 6 is block accordingly. If theinternal combustion engine or its exhaust gas purification systemrequires secondary air, a corresponding secondary air fan (not shownhere) is activated, applying a suitable vacuum to the secondary airoutlet 6 to thereby draw purified fresh air out of the interior 8 of thering filter insert 3. Since the flow path up to the crude air inlet 4 isrelatively short in the inventive intake air filter 1, this additionalfresh air demand leads to relatively little or no pressure drop in theintake tract leading from the filter housing 2 to the internalcombustion engine. In addition, the secondary air has very little or nonegative effect on the sound-absorbing measures in the intake tractbetween the internal combustion engine and the filter housing 2.Accordingly the inventive intake air filter 1 may also be used inprinciple with such an intake system which was originally not designedfor a secondary air supply. To this extent the inventive intake airfilter 1 permits a modular add-on design for the intake system.

1. An intake air filter for an internal combustion engine, in particularin a motor vehicle, comprising a filter housing (2) which has a crudeair inlet (4) and a clean air outlet (5) and comprising a ring filterinsert (3) which is situated in the filter housing (2) and through whichthe air flows radially from the outside to the inside, having a firstend disk (10) on one axial end, said disk having at least one opening(12) through which the clean air outlet (5) communicates with theinterior (8) of the ring filter insert (3), whereby the filter housing(2) has a secondary air outlet (6) on the clean side and whereby thering filter insert (3) has a second end disk (11) on one axial end whichfaces away from the first end disk (10), said second end disk having atleast one opening (17), wherein the secondary air outlet (6)communicates through the opening (17) in the second end disk (11) withthe interior (8) of the ring filter insert (3).
 2. The intake air filteraccording to claim 1, wherein the connection (18) and the second enddisk (11) are manufactured as separate parts, and the connection (18) isinserted into the second end disk (11) and/or is fixedly connected tothe second end disk (11) and/or is welded or glued to the second enddisk (11).
 3. The intake air filter according to claim 1, wherein theconnection (18) is manufactured separately from the second end disk(11), and the connection (18) is fixedly molded or embedded in foam inthe second end disk (11) by injection molding or foaming around a corein the manufacture of the second end disk (11).
 4. The intake air filteraccording to claim 1, wherein the intake connection (18) is integrallymolded on the second end disk (11).
 5. The intake air filter accordingto claim 1, wherein a secondary outlet connection (19) is formed on thefilter housing (2) and is designed to be complementary to the connection(18), and the secondary air outlet (6) communicates with the interior(8) of the ring filter insert (3) through said connection.
 6. The intakeair filter according to claim 5, wherein the secondary outlet connection(19) is integrally molded on the filter housing (2).
 7. The intake airfilter according to claim 5, wherein the secondary outlet connection(19) and the connection (18) cooperate in the manner of a plugconnection when the ring filter insert (3) is inserted into the filterhousing (2).
 8. The intake air filter according to claim 1, wherein amain outlet connection (13) is formed on the filter housing (2), withthe ring filter insert (3) with the opening (12) in the first end disk(10) being attachable to this outlet connection, and the clean airoutlet (5) communicates with the interior (8) of the ring filter insert(3) through this connection.
 9. A ring filter insert for the intake airfilter (1) according to claim 1, having on one axial end a first enddisk (10) which has at least one opening (12) and having a second enddisk (11) on the axial end opposite the first end disk (10), wherein thesecond end disk (11) has a connection (18) which communicates with theinterior (8) of the ring filter insert (3) on the one hand and on theother hand also communicates with a secondary air outlet (6) of thefilter housing (2) in the case of a ring filter insert (3) inserted intoa filter housing (2) of the intake air filter (1).
 10. A ring filterinsert for the intake air filter (1) according to claim 1, having on oneaxial end a first end disk (10) which has at least one opening (12) andhaving a second end disk (11) on the axial end opposite the first enddisk (10), wherein the second end disk (11) has a connection (18 whichcommunicates with the interior (8) of the ring filter insert (3) on theone hand and on the other hand also communicates with a secondary airoutlet (6) of the filter housing (2) in the case of a ring filter insert(3) inserted into a filter housing (2) of the intake air filter (1),characterized by the connection (18) and the second end disk (11) aremanufactured as separate parts, and the connection (18) is inserted intothe second end disk (11) and/or is fixedly connected to the second enddisk (11) and/or is welded or glued to the second end disk (11).
 11. Afilter housing of the intake air filter (1) according to claim 1, havinga crude air inlet (4), a clean air outlet (5) and a secondary air outlet(6) on the clean side, wherein a secondary outlet connection (19) isformed on the filter housing (2), communicating with the secondary airoutlet (6) and being designed to be complementary to the connection(18), whereby the secondary air outlet (6) communicates through thesecondary outlet connection (19) with the interior (8) of the ringfilter insert (3) when the ring filter insert (3) is inserted into thefilter housing (2).
 12. A filter housing of the intake air filter (1)according to claim 1, having a crude air inlet (4), a clean air outlet(5) and a secondary air outlet (6) on the clean side, wherein asecondary outlet connection (19) is formed on the filter housing (2),communicating with the secondary air outlet (6) and being designed to becomplementary to the connection (18), whereby the secondary air outlet(6) communicates through the secondary outlet connection (19) with theinterior (8) of the ring filter insert (3) when the ring filter insert(3) is inserted into the filter housing (2), characterized by thesecondary outlet connection (19) is integrally molded on the filterhousing (2).